Welcome to the AC Tropical Fish aquarium forum. Our aquarium forum is the place to discuss any aquarium related issue in a friendly environment. Our aquarium forum welcomes aquarists of all levels from beginners to experts. Please ask a question in the how to section of our forum or read the FAQ section if you have any questions. register to and become a part of our friendly aquarium forum community today.

Please help!

My pleco has this wound on his stomach. It started out being just an outline of a circle but its getting worse. I am treating with melafix because its an open wound but I honestly have no clue what it even is. Can anyone help?

Additional information would help alot.
How is the pleco, behavior wise? Does he still act normally or does he show strange behavior?
What tank size is the fish in? What is your maintenance routine and what are your water parameters, if you know. What are the fish's tankmates and have you added any recently? Did you do or change anything when the wound formed?

Plecos behavior is normal, size is about six inches living in a 20h with dwarf rainbows, danios, tetras. I just did a 50% h20 change and replaced filters. I haven't checked my ammonia or nitrite levels although I am sure they are fine. I did rearrange the plants I have in my tank to make more room for him. I used to have a giant pirate ship in the middle of the tank but he has gotten kind of large so now I have only plants and the center of the tank is open. More room for the fish in general. It started out as a ring where It kind of looked like he get branded with a little wire and all the skin inside of the ring looked normal. as the past day has progressed the skin in the surrounding circle kind of is getting eaten away.

What do you mean with replace the filters? I surely hope you didn't throw out the sponges and etcetera in them! The bacteria that live there help clean your water, basically the liver and kidneys of a tank. Without them, well, you know what happens to humans with kidney failure.

Melafix is fairly weak, and id only use it for really minor things. For this pleco i would recommend a broad spectrum antibiotic depending on where you live. Change as much water as the medication schedule allows and hope for the best. If you aren't doing so already, feed the pleco with vegetables such as cucumber or spinach, cleaned and pinned down with a fork. There is no way a pleco that size is getting enough food in a 20 gallon without supplemental feeding.

By the ways, if the pleco survives, I would look for a bigger tank to house it, either buy one or find someone who has a 75 or more gallon tank. Common plecos like yours regularly exceed a foot in length, and many have the potential to exceed 1,5 feet. Don't worry about not having a "cleaner fish" in your tank. Waste maintenance is the aquarist's job and a pleco will not help.

Just throwing this out there since nobody has mentioned it yet: HEATER BURN

Id agree, but per the description it sounds like its progressively getting worse and growing. I don't have any experience with fish being burned, but the fact that is growing seems contrary to a burn. It seems like some sort of infection or nasty bacteria. I suppose an infection could have stemmed from a burn though.

110 Gallon New World Cichlid Tank
Tiger Oscar, Large Common Pleco, Blood Red Parrot, A lot of Black Convicts.

First off, what are the water parameters - esp. ammonia? How often and how large are your water changes?

Second, any open wound will need more aggressive treatment than melafix (frankly, a natural med is not very useful. Sorry, but the antibiotic level in a natural product is gonna be near zero.) I would suggest, for a natural treatment, salt (1 tsp per 10 gal combined with raising temp as high as allowed for your fish.) If fungus related, salt and higher temp will help a lot; if bacteria, not as much.

I'd think real antibiotic would work best. Be careful, some of these can crash a filter - get ones that are safe for filter bacteria.

NEVER change a filter (media) when treating a sick fish. Your tank filter will crash. The last thing a sick fish needs is ammonia levels to shoot up. Watch that parameter closely, measure once a day for the next seven to eight days - if zero, than you should be safe. If non-zero than at least 50% water changes every day until the filter bacteria regrow.

Knowledge is fun(damental)

A 75 gal with eight Discus, fake plants, and a lot of wood also with sand substrate. Clean up crew is down to just two Sterba's Corys. Filters: continuous new water flow; canister w/UV, in-tank algae scrubber!! Finally, junked the nitrate removal unit from hell.